Electrical impedance tomography: A compass for the safe route to optimal PEEP.

Setting the proper level of positive end-expiratory pressure (PEEP) is a cornerstone of lung protective ventilation. PEEP keeps the alveoli open at the end of expiration, thus reducing atelectrauma and shunt. However, excessive PEEP may contribute to alveolar overdistension. Electrical impedance tomography (EIT) is a non-invasive bedside tool that monitors in real-time ventilation distribution. Aim of this narrative review is summarizing the techniques for EIT-guided PEEP titration, while providing useful insights to enhance comprehension on advantages and limits of EIT for current and future users. EIT detects thoracic impedance to alternating electrical currents between pairs of electrodes and, through the analysis of its temporal and spatial variation, reconstructs a two-dimensional slice image of the lung depicting regional variation of ventilation and perfusion. Several EIT-based methods have been proposed for PEEP titration. The first described technique estimates the variations of regional lung compliance during a decremental PEEP trial, after lung recruitment. The optimal PEEP value is represented by the best compromise between lung collapse and overdistension. Later on, a second technique assessing alveolar recruitment by variation of the end-expiratory lung impedance was validated. Finally, the global inhomogeneity index and the regional ventilation delay, two EIT-derived parameters, showed promising results selecting the optimal PEEP value as the one that presents the lowest global inhomogeneity index or the lowest regional ventilation delay. In conclusion EIT represents a promising technique to individualize PEEP in mechanically ventilated patients. Whether EIT is the best technique for this purpose and the overall influence of personalizing PEEP on clinical outcome remains to be determined.

Sella N ，Pettenuzzo T ，Zarantonello F ，Andreatta G ，De Cassai A ，Schiavolin C ，Simoni C ，Pasin L ，Boscolo A ，Navalesi P ... -  《-》

Assessment of electrical impedance tomography to set optimal positive end-expiratory pressure for veno-venous ECMO-treated severe ARDS patients.

Ultra-protective ventilation with low tidal volume is used in severe acute respiratory distress syndrome (ARDS) patients under extracorporeal membrane oxygenation (ECMO). However, the optimal positive end-expiratory pressure (PEEP) is unknown. The aim of our study was to assess electrical impedance tomography's (EIT) ability to choose the best PEEP for these patients. A recruitment maneuver and after a decremental PEEP trial from 20 to 5 cmH20 were monitored by EIT, with lung images divided into four ventral-to-dorsal horizontal regions of interest. For each patient, three EIT-based PEEP were defined: PEEP ODCLmin (lowest pressure with the least EIT-based collapse lung [CL] and overdistension [OD]), PEEP ODCL15 (lowest pressure able to limit EIT-based collapse to less than or equal to 15% with the least overdistension) and PEEP Comp (PEEP with the highest EIT-based compliance). High PEEP levels were significantly associated with more overdistension while decreasing PEEP led to more collapsed zones. PEEP ODCL15 and PEEP Comp were in complete agreement with the reference Pulmonary PEEP (chosen according to usual respiratory clinical and ultrasound criteria), PEEP ODCLmin was in average agreement with the Pulmonary PEEP. EIT may be a useful real-time monitoring technique to optimize the PEEP level in severe ARDS patients under ECMO. Ultra-protective ventilation with low tidal volume is used in severe acute respiratory distress syndrome patients under extracorporeal membrane oxygenation (ECMO), but the optimal positive end-expiratory pressure is unknown. This trial shows that electrical impedance tomography may be an interesting non-invasive bedside tool to provide real-time monitoring of PEEP impact in severe ARDS patients under ECMO. The Pulmovista® electrical impedance tomography was provided by Dräger (Lübeck, Germany) during the study period. Dräger had no role in the study design, collection, analysis and interpretation of the data, writing the article, or the decision to submit the article for publication.

Puel F ，Crognier L ，Soulé C ，Vardon-Bounes F ，Ruiz S ，Seguin T ，Fourcade O ，Minville V ，Conil JM ，Georges B ... -  《-》

Bedside Contribution of Electrical Impedance Tomography to Setting Positive End-Expiratory Pressure for Extracorporeal Membrane Oxygenation-treated Patients with Severe Acute Respiratory Distress Syndrome.

Franchineau G ，Bréchot N ，Lebreton G ，Hekimian G ，Nieszkowska A ，Trouillet JL ，Leprince P ，Chastre J ，Luyt CE ，Combes A ，Schmidt M ... -  《-》

Variation of poorly ventilated lung units (silent spaces) measured by electrical impedance tomography to dynamically assess recruitment.

Spadaro S ，Mauri T ，Böhm SH ，Scaramuzzo G ，Turrini C ，Waldmann AD ，Ragazzi R ，Pesenti A ，Volta CA ... -  《CRITICAL CARE》

Targeted lateral positioning decreases lung collapse and overdistension in COVID-19-associated ARDS.

Mlček M ，Otáhal M ，Borges JB ，Alcala GC ，Hladík D ，Kuriščák E ，Tejkl L ，Amato M ，Kittnar O ... -  《-》